1. Field of the Invention
The present invention generally relates to a method for manufacturing an electronic part such as a hybrid integrated circuit, etc.
2. Description of the Prior Art
A recent increased need for utilization of electronic parts has consequently given much importance to the method for manufacturing electronic parts.
One example of a conventional method for manufacturing electronic parts will be described with reference to the flow chart of FIG. 3a. The flow chart of FIG. 3a shows the sequence of operations in the conventional manufacturing method of electronic parts. A hybrid integrated circuit board 1 of FIG. 3b (hereinafter referred to as an HiC board) which is a ceramic board in the present example, is finished by printing and baking. A creamy solder 2 is deposited onto the HiC board 1 for securing chip parts 3 and a terminal wire carrying strip 5 wherein a plurality of terminals are mounted in parallel on a strip member to form a succession of terminal wires like the teeth of a comb along the length of the strip member. The HiC board 1 is divided into parts 4. The terminal wire carrying strip 5 having its own length and independent of each part 4 has the terminal wires connected to the HiC board 1 by the creamy solder 2.
The conventional manufacturing method referred to above includes 10 operations as follows.
In the first step T1, a circuit pattern is printed on the HiC board 1 by a paste-like conductor, and then the HiC board 1 and the conductor are heated to securely bake a conductive circuit 23 onto the HiC board 1.
In the second step T2, the creamy solder 2 is printed on the portions of the HiC board 1 where the chip parts 3 are to be mounted and the wires from the terminal wire carrying strip 5 are to be connected.
In the third step T3, the chip parts 3 are mounted onto the printed creamy solder 2.
In the fourth step T4, the HiC board 1, the creamy solder 2 and the mounted chip parts 3 are heated, and accordingly, the creamy solder 2 is melted, so that the chip parts 3 and the HiC board 1 are mechanically connected to each other, that is, reflow soldering is carried out.
In the fifth step T5, a semiconductive element 22 is fixed onto the HiC board 1 by a bonding agent (not shown), that is, die bonding is carried out.
In the sixth step T6, the semiconductive element 22 which has been securely bonded onto the HiC board 1 in the fifth step is mechanically connected to the conductive circuit 23 on the HiC board 1 by a fine wire (not shown) made of gold or aluminum, namely wire bonding is carried out.
In the seventh step T7, a protective agent is coated on the board for protecting the semiconductive element 22 and the fine wire connecting the semiconductive element 22 and the conductive circuit 23, and is then thermally hardened.
In the eight step T8, the HiC board 1 is divided into parts of a predetermined size.
In the ninth step T9, the terminal wires on the terminal wire carrying strip 5, which are provided for electrical connection with an external circuit, are subjected to reflow soldering by melting the creamy solder 2 in a reflow furnace.
Finally, in the tenth step T10, a number is marked on a predetermined position on the HiC board 1 by an ultraviolet hardening ink (not shown), and the ink is hardened through irradiation by ultraviolet rays (UV hardening), thereby to complete the electronic part.
In the above-described flow of operations, however, at least two reflow furnaces are required, one for securing the chip part onto the HiC board and one for connecting the terminal wires to the HiC board. Moreover, the abovedescribed prior art necessitates transfer and mounting devices to be provided respectively for the HiC board and for the terminal wire carrying strip. As a result, the manufacturing apparatus is inevitably bulky and expensive. Furthermore, the HiC board is subjected to many heating and cooling operations in the two reflow furnaces, resulting in distortion of the HiC board and consequently in such disadvantages that good product accuracy is difficult to achieve, and the yeld is reduced.